Computer vision based tracking systems are currently used in various applications such as, gesture controlled man machine interfaces, security systems and video game consoles. Different sensors may be used to track moving objects.
A typical body tracking system tracks certain body features (or markers attached to the body) using a camera and processor. The camera obtains images of the body and the processor derives the position of the body feature from the images. The camera generated image frame is then associated with a target, typically a display which may be associated with a computer. For example, in a computer vision based system for controlling a device through human gestures a camera is used to obtain images of a user and track movement of the user's hands, for example, and translates the user's hand movements to control the device, for example, to activate icons on a computer's desktop.
Camera image frames, as well as targets, such as computer displays are typically rectangular. But often the range of natural human limb movement is not rectangular. For example, when a person is standing and moving his arms, the movement range or field of movement possible for the person's arms is an area similar to a circle or ellipse. Thus, a person may not easily reach all the spots of a rectangular target (e.g. if a person can easily reach the top of a rectangular frame using his arms, he will have difficulties reaching the corners of that frame). In other words, a person stretching his arm to the limit of his field of movement may not be able to reach the limit of a target. The same may be true for animal or robotic machine movement. Thus, the association or alignment of an image frame with a target may result in less than accurate positioning of tracked objects (such as a user's hand) on the target since this alignment does not account for the difference between the shape of the field of movement of the object and the shape of the target.
Images can be processed to change their size or shape. Complex algorithms are typically used for such image transformations since adjacent pixels must be considered when changing the size or shape of an image and interpolation is often used, which may reduce overall image definition and which involves high computing power.
To date there is no simple method for accurately translating the relative position of an object in a certain shaped field of movement to a differently shaped target. Such a method is especially missing in the field of interactive computer games.